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+-- Forum: Pulse Sequences (Basic) (/forumdisplay.php?fid=5)
+--- Forum: Fat-Water Methods (/forumdisplay.php?fid=42)
+--- Thread: sth about DIXON (/showthread.php?tid=10212)
sth about DIXON - fungfung310@gmail.com - 06-03-2016 09:47 AM
Hi, I am new to MRI and I find this website very useful ! I would like to ask sth about DIXON and india Ink.
In the India ink page, to my understanding, it is just obtaining OOP images .
it showed that OOP only happens when there is fat and water coexist in the voxel. if there is pure fat or pure water, OOP wont happen. That how india ink is formed
So when it comes to DIXON, a pure fat or water should show the same intensity in both IP and OOP, so in DIXON fat only image wont cancel out each others ???? and only voxel coexist fat and water show fat signal ???
I am not an expert in human anatomy, Could I assume, macroscopically there are no pure fat or water in human body , so fat always coexist with water and DIXON could work
RE: sth about DIXON - aelster - 06-04-2016 05:29 PM
Dear Fungfung310,
Your statements about the Dixon method and india ink artifact are all correct. Phase cancellation only occurs in voxels that contain both water and fat when the echo time is appropriate for the OOP condition to occur. Voxels containing pure water or pure fat are not affected.
In the human body there are many areas containing pure water -- the cerebral ventricles containing CSF and bladder containing urine are obvious candidates. Many tissues like the brain are predominantly water but contain fat in the form of phospholipids and sphingolipids (myelin). These lipids have very short T2 values and are not visualized on conventional MR pulse sequences, so the brain may be considered to be pure water. Finding pure fat is difficult -- Adipose tissue is predominantly lipid but also contains blood vessels and lymphatics with some water in it.
Hope this helps.
ADE
RE: sth about DIXON - fungfung310@gmail.com - 06-04-2016 09:10 PM
Thanks very much, it helps a lot !